opensource wide area san?

[Michael Butash]

Well, don't "have" to use DFS per say, but it might be easiest if you're
native windows.  If you do, specifically look at 2003 R2's DFS-R as
supposedly it fixes most/all the shortcommings of FRS, replacing and
relegating it only to sysvol duties.  This still won't help iscsi raw
volumes hosted off OF.  DRDB is most definitely a high-speed lan (read
gig) technology though, not something to throw on top of T1's as the
data would consistently be out of date and/or never fully finish.

What it comes down to is bandwidth, and you don't have a lot to work
with if you're only talking 2x t1's.  Honestly for what you're paying
for T1's you can probably get a 10mb ethernet drop site to site locally
(in-city) at least to help with it.  Metro Ethernet is typically cheaper
than maintaining legacy TDM technologies anymore for carriers, so I've
seen some renegotiate contracts that worked out cheaper to roll to it
Ethernet (hardware for 10/100/100 ethernet is obviously cheaper than a
T1 too).  Otherwise talk to your carriers about mpls services with metro
ethernet at either end if distance or differing carriers are an issue,
it can actually cheapen the costs for carriers to exchange an IP session
than tying up a clear/frame ds1 interstate with associated tariffs and
other carrier pricing manipulation.

If increasing bandwidth isn't an option, you can schedule your file
replication asynchronously at low-bandwidth times, it might work too,
but you still might not have enough time/bandwidth to replicate your
whole volume set in "off-peak" hours.  All the workarounds and hacks in
place, you might just realize you need more bandwidth to do what you
want to do anyways.

Enterprise WAN accelerators like Cisco can transparently "cache" and
replicate files remotely within a cloud of site to minimize
bandwidth/maximize availability, but isn't exactly a full DR solution
for your data - this is performance related only, but might somewhat
work for you.  There are a lot of commercial applications for this as
well, most getting pricey rather fast.  

If it's truly full DR replication you seek, some things have got to
give.  This is the kind of thing that typically gets me looking at
1-10gig pipes on a wan...

-mb


On Thu, 2009-07-30 at 17:09 -0700, Stephen wrote:
> This si kind of what we have...
> 
> "Is the environment use windows DFS or anything?  FRS was crap, but DFS-R
> (R2) might provide adherence to bandwidth limits on site-based
> replication.  I'm looking at giving iscsi targets to windows off a local
> san (OF), and giving DFS-R a try to manage replications and such, just
> not sure how it stretches yet.  Not positive, but worth a look if DFS is
> front-ending a windows server/client environment for your needs,
> supposedly it has wan-friendly qualities for such occasion.  Doesn't
> solve all issues, but may in some cases."
> 
> and it performs really well except when i do large data xfers from
> machine 1 and machine 2 with main data volumes as iSCSI on the same OF
> server.
> 
> but that one is kind of expected.
> 
> we are really having to go back to DFS/FRS i was just trying to
> explore options but for only2-3 more months of this its at this point
> just better to fix DFS again.
> 
> however i still like OF as a filer.
> 
> On Wed, Jul 29, 2009 at 8:27 PM, Michael Butash<michael at butash.net> wrote:
> > Consider also Qos on the routers at very least, segregate your traffic
> > via CBWFQ (Cisco) or whatever vendor solution supports queuing.  You
> > don't want disk sync's to swat other important traffic.
> >
> > Is the environment use windows DFS or anything?  FRS was crap, but DFS-R
> > (R2) might provide adherence to bandwidth limits on site-based
> > replication.  I'm looking at giving iscsi targets to windows off a local
> > san (OF), and giving DFS-R a try to manage replications and such, just
> > not sure how it stretches yet.  Not positive, but worth a look if DFS is
> > front-ending a windows server/client environment for your needs,
> > supposedly it has wan-friendly qualities for such occasion.  Doesn't
> > solve all issues, but may in some cases.
> >
> > -mb
> >
> >
> > On Wed, 2009-07-29 at 14:06 -0700, Stephen wrote:
> >> We are useing an openfiler server here and it has been running great.
> >>
> >> right now it is hosting several iSCSI connections to our servers
> >> however we need to replicate data on one of the iSCSI volumes between
> >> 2 sites.
> >>
> >> internally using DRBD/heartbeat comes to mind as a new but no brainer
> >> solution. however these servers need to live in 2 different states
> >> (and eventually maybe 3-4 locations)
> >>
> >> generally it would seem that rsync would be better however it is a
> >> file level replication and seems that it would not be able to
> >> replicate the iSCSI volume which is block level...
> >>
> >> can DRBD/heartbeat sync across a t-1 or pair of bonded t-1's? or will
> >> it eat the pipe?
> >>
> >
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> 
>